The principal objectives of this study are to determine those factors associated with the capacity of MCMV to induce CNS infection and to determine mechanisms by which CNS infection can be prevented by immunization. Current studies are particularly concerned with two strains of MCMV which differ in their virulence for mice; the more virulent is a harvest of infected CD-1 salivary glands, the other a harvest of the salivary glands of C57B16 mice (a second pass). The means by which protection is conferred to suckling animals by immune nursers is being explored by administering 'immune' T cells, B cells, macrophages and immunoglobulins IP to non-immune nursers.